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                                 CERT-Renater

                      Note d'Information No. 2004/VULN099
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DATE                      : 10/03/2004

HARDWARE PLATFORM(S)      : IBM.

OPERATING SYSTEM(S)       : AIX 4.3.3.
                            
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VULNERABILITY SUMMARY

VULNERABILITY: Vulnerability in rexecd may allow root access

PLATFORMS: AIX 4.3.3

SOLUTION: Apply the APAR listed below.

THREAT: A remote attacker may gain root privileges.

CERT VU Number: n/a
CVE Number: n/a
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DETAILED INFORMATION


I. Description
===============
A vulnerability was discovered in the rexecd daemon that may allow
remote user to gain root privileges.

This vulnerability can cause user information of the connecting user
to be potentially be overwritten with that of another user. The
connection would proceed with the overwritten data and the connecting
user would then have the privileges of the other user.

This may be dependent on the type of authentication defined for the
connecting user. It is possible, but not certain, that the connecting user
may gain root privileges.

Note that this only applies to AIX 4.3.3.

rexecd ships as part of the bos.net.tcp.client fileset. To determine if
this fileset is installed, execute the following command:

# lslpp -L bos.net.tcp.client

This vulnerability is in filesets 4.3.3.91 and below.



II. Impact
==========

A remote attacker may gain root privileges.



III. Solutions
===============

A. Official Fix
IBM provides the following fixes:

APAR number for AIX 4.3.3: IY53507

NOTE: Affected customers are urged to upgrade to 5.1.0 or 5.2.0 at
the latest maintenance level.


B. Workaround
The rexec daemon runs under the control of the inetd daemon.
To disable the rexecd daemon, as root enter:

# smitty rminetdconf

Scan through the list of subservers. If rexecd is not
listed it is not enabled. If it is listed, place the cursor
on the name and press enter.

To make the change effective enter:

# refresh -s inetd



IV. Obtaining Fixes
===================

AIX Version 4.3.3 and Version 5 APARs can be downloaded from
the eServer pSeries Fix Central web site:

http://www-912.ibm.com/eserver/support/fixes/fcgui.jsp

Security related Emergency Fixes can be downloaded from:

ftp://aix.software.ibm.com/aix/efixes/security


V. Acknowledgements
===================

This document written by Kent Stuiber.



VI. Contact Information
========================

If you would like to receive AIX Security Advisories via email, please visit:
https://techsupport.services.ibm.com/server/pseries.subscriptionSvcs

Comments regarding the content of this announcement can be directed to:

security-alert@austin.ibm.com

To request the PGP public key that can be used to communicate securely
with the AIX Security Team send email to security-alert@austin.ibm.com
with a subject of "get key". The key can also be downloaded from a
PGP Public Key Server. The key id is 0x3AE561C3.

Please contact your local IBM AIX support center for any assistance.

eServer is a trademark of International Business Machines Corporation.
IBM, AIX and pSeries are registered trademarks of International Business
Machines Corporation. All other trademarks are property of their
respective holders.

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